The basics of casino gambling are actually quite simple. Although the rules are different for each game, the basic principle is essentially the same for everyone. Be it a round of blackjack, a spin of the roulette wheel, a throw at the craps table or a round of slot machines – players make a bet and bet against the casino (also known as the house). If the players lose, the house takes their stake. If the players win, the house pays its share.

That’s pretty much all you need to know to start playing in the casino. Of course, you also need to know the rules for each specific game you want to play, but these are usually relatively easy to learn. However, in our opinion, it is at least worth having a basic understanding of how casino gambling works.

In particular, you should understand how casinos make money and become familiar with the house edge concept and payout percentages. You should also understand why it is possible for players to win money even when the odds are against them. On this page we explain all of these things.

How casinos make money

In essence, all casino games are games of chance, which means that a player is ultimately dependent on luck. There are some games where an element of skill also plays a role, like blackjack, but luck is usually the primary factor in determining whether a player wins. However, this doesn’t mean that a casino needs luck to get a profit from the people who play their games.

Each individual game offers a house edge in the long term and so money is earned.

The advantage that is effectively integrated into every casino game is called house edge or bank edge. This advantage means that a casino always wins money over time. The house edge exists because casinos don’t pay winning bets according to the real odds of that bet. Technically, they make money every time a player bets for money.

Although the house does not win every single bet, the odds are mathematically speaking in their favor. This is why casino games are known as negative expectation games because the long term expectation is negative.

The house edge

We now use an example to show how the banking advantage works in practice. Let’s take a bet of £1 on a single number for every spin when playing roulette. A roulette wheel has either 37 or 38 numbers, depending on whether you are playing American or European style. So there is either a 1 in 37 or a 1 in 38 chance of winning the bet. We use the European version in this example.

In theory, you would expect to win the bet once every 37 spins. In practice, it doesn’t quite work because of the standard deviation and variance that we’ll explain a little later, but in the long run, every number should come about once every 37 spins. For this example, we work on the basis that each number appears exactly once every 37 spins.

If a casino offered true odds on roulette, players would neither win nor lose in the long run and the casino would not make any money. Casinos are in the business of making money, so the house edge is very important to operators.

House edge versus percentage

With 37 spins you bet £37. In theory, you get £0 on 36 of these spins and £37 win on a spin.

£ is 2.7% of £37. That means the house edge in this game is 2.7%.

The house edge / payout percentage is the same regardless of the bet you place on the game. This means that for every £100 wagered on roulette, the theoretical house win is £2.70. While a casino would never make exactly £2.70 per £100 wager, it would amount to over a million spins on average.

It should be noted that the house edge is not the same in every casino game and it is an obvious advantage to play where the advantage is small. The lower the house edge, the less you will theoretically lose over time. The size of the house edge is therefore something you should consider when deciding which games to play. But it shouldn’t be the only consideration, as some of the games with higher house edge also offer certain advantages.

How players win in casinos

We have shown above that the casino always wins in the long run. You may think that playing casino games is pointless because you can never win. However, it is quite possible to win in casinos despite the house edge. This is because it takes millions of bets for the house edge to balance itself out and there is absolutely no reason why a player shouldn’t overcome the advantage in the short term.

Let’s go back to the example above, where you bet £1 on a single number in roulette. With this method, there are also a number of possible outcomes that you can use to win money with house edge:

Win on the first rotation of the wheel

This is a result that is conceivable and would immediately give you profits of £35. If you stop right away, you’re in the plus. Even if you play another 20 spins with no winnings, you can still stop winning.

Forecasted numbers come more than expected

Let’s say you played 100 spins and your number came five times, you’d be good in plus. You would have lost 95 times, a total of £95, but the five times you won brought you £175. Your total winnings would be £80 (£175 -95).

It doesn’t matter which game you play – the fact is that there is always a chance that you can make money. Take black jack, for example. It is quite possible to win several hands in a row in blackjack, and it is far from unusual for players to have extended winning streaks. Then there are slot machines. You could only play a few euro slots and win thousands or even hundreds of thousands. You would need a lot of luck, of course, but it could happen.


The essence of casino games is that the odds are ultimately against you, but there is always a chance that you can disrupt the odds. You never know exactly what’s going to happen, but it’s always pleasant to learn, and that’s what makes casino games so exciting.